Copper oxalate complexes

ABSTRACT

A cuprous oxalate complex of the formula Cu 2  (CO) n  L m  C 2  O 4  wherein L is an unsaturated hydrocarbon containing at least one non-aromatic unsaturation and n and m are numbers from 0 to 2.

BACKGROUND OF THE INVENTION

This invention relates to copper(I) oxalate complexes. Moreparticularly, the copper(I) oxalate complexes contain CO and/orunsaturated hydrocarbons as ligands.

U.S. Pat. No. 2,604,391 discloses a gas-producing charge for use in anon-detonating decomposition. The composition contains nitroguanidine orguanidine nitrate and a copper compound such as copper powder, cupricoxide, cuprous chloride or cuprous oxylate. A. P. Glaskova,Explosivstoffe, 23,137-145(1973) describes the effects of catalysts onthe deflagration of certain classes of explosives. Cu₂ C₂ O₄ and itseffects on ammonium perchlorate are shown in FIG. 8 and Table V.

It is known that certain copper(I) salts form complexes with olefins andacetylenes. For example, cuprous chloride is known to form complexeswith both ethylene and acetylene. U.S. Pat. No. 3,401,112 teaches amethod of separating a mixture of hydrocarbons having differing degreesof unsaturation using a copper(I) salt of the formula CuXA where XA isan anion, X is oxygen or fluorine and A is the remainder of the anion.In general, anions of the cuprous salts are anions of inorganic, organicor organo-inorganic acids, wherein the pK_(a) values are in the order of4.6 or less. CuXA forms a cuprous complex with said unsaturatedhydrocarbon. U.S. Pat. Nos. 3,754,047 and 3,755,487 disclose a processfor separating complexible ligands such as olefins, acetylenes,aromatics and CO from a feed-stream using cuprous salts such as CuAlCl₄,CuBF₄, CuOOCCF₃, CuPF₆ and the like.

It is also known that certain cuprous salt solutions will absorb CO. Areview of the early literature may be found in J. Appl. Chem. (London),15, 17-28 (1965). U.S. Pat. No. 4,048,292 describes a process forrecovering CO from CO₂ -free gas streams using an absorber solutioncontaining a copper ammonium C₁₋₂ acylate.

SUMMARY OF THE INVENTION

It has been discovered that cuprous oxide can react with oxalic acid andcarbon monoxide to form a novel cuprous carbonyl oxalate complex whereinthe carbonyl may be displaced by an unsaturated ligand. The newcomposition of matter comprises a cuprous oxalate complex of the formulaCu₂ (CO)_(n) L_(m) C₂ O₄ where L is an unsaturated hydrocarboncontaining at least one non-aromatic unsaturation capable of forming aCu-L bond and n and m are numbers from 0 to 2. In one preferredembodiment n is 2 and m is 0. In another preferred embodiment, n is 0 or1 especially 0 and m is from 1 to 2.

In another aspect of the invention Cu₂ C₂ O₄ and Cu₂ (CO)₂ C₂ O₄ may beprepared by a process which comprises contacting Cu₂ O and oxalic acidwith carbon monoxide in an inert organic solvent. With regard to thepreparation of Cu₂ (CO)₂ C₂ O₄, Cu₂ C₂ O₄ may be isolated as anintermediate depending on the choice of solvent. Moreover, by contactingCu₂ (CO)₂ C₂ O₄ with an unsaturated hydrocarbon ligand containing atleast one non-aromatic unsaturation, the CO may be partially or whollydisplaced.

DETAILED DESCRIPTION OF THE INVENTION

Cupric oxalate is a well-known copper(II) complex. Cuprous oxalatecomplexes, however, cannot be prepared by ordinary methods, e.g.,reacting Cu₂ O and oxalic acid in aqueous solution. The presentinvention relates to the discovery that if the reaction between Cu₂ Oand oxalic is carried out in an inert organic solvent in the presence ofcarbon monoxide, copper(I) oxalate complexes can be isolated in highyields.

Suitable inert organic solvents are ethers, saturated hydrocarbons,aromatic hydrocarbons, esters, amines, ketones and sulfolanes. Preferredsolvents are ethers and saturated aliphatic hydrocarbons substituted byhalogen. Depending on the specific solvent employed, Cu₂ C₂ O₄ may beisolated as an intermediate. For example, if Cu₂ O is reacted withoxalic acid in the presence of CO and diethyl ether as solvent, Cu₂ C₂O₄ is obtained in nearly quantitative yield. On prolonged contact withCO, Cu₂ C₂ O₄ is converted to Cu₂ (CO)₂ C₂ O₄. On the other hand, iftetrahydrofuran is substituted for diethyl ether, Cu₂ (CO)₂ C₂ O₄ isformed directly.

The reactants are combined in approximately stoichiometric amounts,i.e., about 1 mole of Cu₂ O per each mole of oxalic acid. CO ispreferably present in excess amounts of about 1.1 to 10 moles or moreper mole of Cu₂ O. Stoichiometric amounts also may be employed. An inertatmosphere is preferred since significant amounts of oxygen may lead tooxidation of the copper(I) complex.

Reaction temperatures may range from about -100° to +100° C. It shouldbe noted that at elevated temperatures, CO is released from the cuprousoxalate complex according to the reaction Cu₂ (CO)₂ C₂ O₄ ⃡Cu₂ C₂ O₄+2CO. Therefore, elevated temperatures may lead to decreased yields.Preferred temperatures are accordingly from about 0° to about 40° C.

When Cu₂ (CO)₂ C₂ O₄ is contacted with unsaturated hydrocarbon L in theinert organic solvents described above, CO is displaced as illustratedby the following equilibria:

    Cu.sub.2 (CO).sub.2 C.sub.2 O.sub.4 +L⃡Cu.sub.2 (CO)LC.sub.2 O.sub.4 +CO

    Cu.sub.2 (CO)LC.sub.2 O.sub.4 +L⃡Cu.sub.2 L.sub.2 C.sub.2 O.sub.4 +CO

In some cases, non-stoichiometric complexes containing L may beobtained, e.g., Cu₂ (diphenylacetylene)₁.5 C₂ O₄. Depending onthermodynamic considerations and reaction conditions, either a mixedcomplex containing CO and L or a fully displaced complex containing onlyL may be obtained. Preferred temperatures for the displacement reactionare from 25° to 150° C. It is also desirable to have a molar excess of Lover Cu₂ (CO)₂ C₂ O₄ with excesses up to 100 fold or more beingpreferred.

Alternatively, Cu₂ L_(m) C₂ O₄ where m is a number from 1 to 2 may beprepared directly by contacting Cu₂ O, oxalic acid and unsaturatedhydrocarbon L in an inert organic solvent with stirring. The red colorof Cu₂ O gradually disappears, and Cu₂ L_(m) C₂ O₄ is isolated uponevaporation of solvent. This preparative technique, however, is notsuitable for low molecular weight unsaturated hydrocarbons, e.g.,ethylene and acetylene.

Preferred L are unsaturated hydrocarbons containing at least oneethylenic, acetylenic or isonitrilic unsaturation, more preferably C₂-C₃₀ alkene, C₂ -C₃₀ alkyne, C₈ -C₃₀ arylalkene, C₈ -C₃₀ arylalkyne, C₄-C₁₄ cycloalkene or isonitrile of the formula R--N.tbd.C where R is C₁-C₂₀ alkyl, C₃ -C₁₂ cycloalkyl, C₇ -C₂₀ aralkyl or C₆ -C₁₀ aryl, andmost preferably C₂ -C₂₀ alkene, C₂ -C₂₀ alkyne, C₈ -C₂₀ arylalkene, C₈-C₂₀ arylalkyne, C₄ -C₁₀ cycloalkene or isonitrile of the formulaR--N.tbd.C where R is C₁ -C₁₀ alkyl, C₆ -C₁₀ cycloalkyl, C₇ -C₁₄ aralkylor C₆ -C₁₀ aryl.

Cu₂ (CO)_(n) L_(m) C₂ O₄ and methods of preparation thereof are usefulin a process for separating CO and L from gas mixtures. When a gasstream containing CO is contacted with Cu₂ O and oxalic acid in an inertorganic solvent, CO is selectively removed by forming the Cu₂ (CO)₂ C₂O₄ complex. CO may be regenerated by merely heating the solvent mixture.The resultant Cu₂ C₂ O₄ solvent mixture can then be recycled foradditional reaction with CO. Cu₂ (CO)₂ C₂ O₄ may also be contacted witha feedstream containing L whereby L is removed by a CO displacementreaction.

The invention is further illustrated according to the followingexamples:

EXAMPLE 1

A flask equipped with a dropping funnel and a gas bubbler was chargedwith 2.86 g of Cu₂ O and 75 ml of tetrahydrofuran (THF). A solutioncontaining 1.80 g oxalic acid in 50 ml THF was added dropwise over a 30minute period while a stream of CO was bubbled through the mixture. Thered color of Cu₂ O changed to a whitish color over a period of 4 hours.The insoluble Cu₂ (CO)₂ C₂ O₄ was isolated by filtration andcharacterized by elemental analysis and infrared (IR) spectroscopy.

EXAMPLE 2

The procedure of Example 1 was followed except that diethyl ether wassubstituted for THF. When CO was bubbled into the red Cu₂ O containingmixture, a color change to grey-violet was observed after several hours.A nearly quantitative yield of Cu₂ C₂ O₄ was obtained. The product wascharacterized by elemental analysis and IR spectroscopy. Prolongedcontact of Cu₂ C₂ O₄ with CO results in conversion to Cu₂ (CO)₂ C₂ O₄.

EXAMPLE 3

A mixture of 2.86 g Cu₂ O, 14.24 g diphenylacetylene and 75 ml CH₂ Cl₂was stirred at room temperature while a solution of 1.80 g oxalic acidin 50 ml CH₂ Cl₂ was added dropwise over a period of 30 minutes. Themixture was then stirred an additional four hours during which time thered color of the Cu₂ O gradually changed to white. The insolublematerial which was isolated by filtration was analyzed and found to havethe composition Cu₂ (C₆ H₅ C.tbd.CC₆ H₅)₁.5 C₂ O₄. The complex wasfurther characterized by infrared spectroscopy.

EXAMPLE 4

An experiment identical to that described in Example 3 was carried outexcept that 4.36 g cyclohexylisonitrile was substituted for thediphenylacetylene. In this case the Cu₂ O gradually dissolved and aclear solution was obtained. By evaporation under vacuum, a whitecrystalline material was isolated. This material was recrystallized froma methylene chloride-pentane mixture and identified as ##STR1## byelemental analysis and infrared and n.m.r. spectroscopy.

EXAMPLE 5

Ethylene gas was bubbled through a suspension of 2.71 g Cu₂ (CO)₂ C₂ O₄in 100 ml THF for several hours at room temperature. After this periodthe suspended solids were isolated by filtration. This product wasidentified as Cu₂ (CO)(C₂ H₄)C₂ O₄.

EXAMPLE 6

A mixture of 2.71 g Cu₂ (CO)₂ C₂ O₄, 2.54 grams 1-hexene and 100 ml CH₂Cl₂ was heated at reflux for several hours under nitrogen. After thisperiod the suspended solids were filtered off and dried under vacuum.This complex has the composition Cu₂ (1-hexene)₁.5 C₂ O₄.

EXAMPLE 7

A mixture of 2.71 g Cu₂ (CO)₂ C₂ O₄ and 1.84 g norbornadiene in 100 mlCH₂ Cl₂ was refluxed for four hours under nitrogen. The solid materialwas recovered by filtration and was characterized as ##STR2##

EXAMPLE 8

In the same manner as described in Example 7, 2.71 g Cu₂ (CO)₂ C₂ O₄ wasreacted with 1.88 g norbornylene forming ##STR3## In addition, a smallamount of a soluble complex with the composition ##STR4## was obtained.

EXAMPLE 9

A mixture of 2.71 g Cu₂ (CO)₂ C₂ O₄ and 4.32 g 1,5-cyclooctadiene (COD)in 100 ml CH₂ Cl₂ was heated to reflux for four hours under nitrogen.The insoluble Cu₂ (CO)₂ C₂ O₄ gradually went into solution. Aftercooling, the mixture was filtered to remove a small amount of residualsolids and the clear filtrate was partially evaporated under vacuum togive a white microcrystalline precipitate. This was analyzed to be Cu₂(COD)₁.5 C₂ O₄.

What is claimed is:
 1. A composition of matter comprising a cuprousoxalate complex of the formula Cu₂ (CO)_(n) L_(m) C₂ O₄ where L is anunsaturated hydrocarbon containing at least one non-aromaticunsaturation capable of forming a Cu-L bond and n and m are numbers from0 to 2, provided that n and m cannot both be
 0. 2. The composition ofclaim 1 wherein n is 0 or 1 and m is from 1 to
 2. 3. The composition ofclaim 2 wherein L is an unsaturated hydrocarbon containing at least oneethylenic, acetylenic or isonitrilic unsaturation.
 4. The composition ofclaim 2 wherein L is C₂ -C₃₀ alkene, C₂ -C₃₀ alkyne, C₈ -C₂₀ arylalkene,C₈ -C₃₀ arylalkyne, C₄ -C₁₄ cycloalkene or isonitrile of the formulaR--N.tbd.C where R is C₁ -C₂₀ alkyl, C₃ -C₁₂ cycloalkyl, C₇ -C₂₀ aralkylor C₆ -C₁₀ aryl.
 5. The composition of claim 2 wherein L is C₂ -C₂₀alkene, C₂ -C₂₀ alkyne, C₈ -C₂₀ arylalkene, C₈ -C₂₀ arylalkyne, C₄ -C₁₀cycloalkene or isonitrile of the formula R--N.tbd.C where R is C₁ -C₁₀alkyl, C₆ -C₁₀ cycloalkyl, C₇ -C₁₄ aralkyl or C₆ -C₁₀ aryl.
 6. Thecomposition of claim 2 wherein n is
 0. 7. A composition of mattercomprising Cu₂ (CO)₂ C₂ O₄.
 8. A process for preparing Cu₂ C₂ O₄ and Cu₂(CO)₂ C₂ O₄ which comprises contacting about equimolar amounts of Cu₂ Oand oxalic acid with CO in an inert organic solvent at temperatures offrom -100° to +100° C.
 9. A process for preparing Cu₂ (CO)_(n) L_(m) C₂O₄ where n is 0 or 1, m is from 1 to 2 and L is an unsaturatedhydrocarbon containing at least one non-aromatic unsaturation whichcomprises contacting Cu₂ (CO)₂ C₂ O₄ with at least an equimolar amountof L in an inert organic solvent at a temperature sufficient to displaceCO with L.